Conventional synchronization techniques used between base stations rely on GPS signals, which broadcast precision time stamps as well as a 1 Hz reference signal. Base stations can extract this timing information through a demodulation process and use them to acquire accurate time as well as the frequency reference needed for training local oscillators, such as VCXOs or OCXOs, whose accuracy, although quite accurate, by itself is not accurate enough for use in base stations. With the expected proliferation of smaller-sized base stations—henceforth we refer them collectively as ‘microcell’ base stations—GPS-based solutions could be either (1) too expensive an option if the microcell base station were to contain a separate GPS receiver, or (2) unavailable due to the environment in which the microcell base station is located. The only other alternative carrier synchronization methodology accurate enough to meet the needs of 4G and beyond is Precision Time Protocol (PTP) defined in the IEEE 1588 standard. PTP based on IEEE 1588 relies on availability of Ethernet through a wireline access, which may not always be available for a given microcell environment. For instance, a standalone microcell that also provides a back-haul communication link to the macro base stations could be located somewhere without a wired Ethernet access and in need of a synchronization method.
Accordingly, there is a need for improved RF synchronization and phase alignment systems and methods.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.